Loosen the hex head screws that fasten the starting mechanism to the chainsaw by turning them counterclockwise. Pull the mechanism off the chainsaw.
Push the cord near the handle so its knot comes out the other end. Untie the knot and pull the handle off the cord.
Lay the starting mechanism on a work bench and remove the "C" clip that holds the recoil to the case. This is done by prying the "C" clip backward with a screwdriver.
Pull off the large washer, spring and starter pause and carefully remove the spool. Try not to disturb the spring underneath.
Pull the spring carefully from the housing with you hands as to not allow it to unspool.
Insert the new recoil spring in the same orientation as the original one and reassemble the starting mechanism, reversing the process used to remove it.